Use of Cultural Filtrates of Certain Microbial Isolates for Powdery Mildew Control in Squash

Powdery mildew induces significant losses in yield and quality of squash. Therefore, culture filtrates of certain microbial isolates, (Epicoccum nigrum, Epicoccum minitans, Epicoccum sp., Trichoderma harzianum, Trichoderma viride and Bacillus pumilus) were used alone, and in combination with the fungicide penconazole to control powdery mildew in squash, under field conditions. Moreover, GC-MS analysis was carried out to identify the chemical components of the most effective culture filtrates against powdery mildew pathogen. The results showed that culture filtrates of different microbial isolates (except for Trichoderma harzianum) were more effective against powdery mildew in squash than the tested fungicide alone at the recommended levels, in both tested seasons. The results also showed that mixing different culture filtrates with penconazole improved efficiency against powdery mildew compared to using the fungicide alone, in both tested seasons. The efficacy of the culture filtrates of the tested microbial isolates against powdery mildew were due to the presence of a mixture of known antifungal compounds. The results suggest the possible use of the culture filtrates of the tested microbial isolates as alternative to fungicides, in powdery mildew control. Also, this study suggests the possible mixing of the culture filtrate of the tested biocontrol agents with fungicides to minimize the applied amount of fungicides.